Spectrometric measurement devices, such as fluorescence measurement devices or absorbance determination devices, are a type of system for detecting or determining an objective component in a sample by a spectroscopic method.
A fluorescence measurement device normally has an excitation spectroscopic system for separating a predetermined wavelength of light from the light generated by a light source and irradiating a sample with the separated light as excitation light, a fluorescent spectroscopic system for separating a predetermined wavelength of light from the light emitted from the sample upon irradiation with the excitation light, and a photodetector for detecting the light separated by the fluorescent spectroscopic system and producing a signal corresponding to the amount of the detected light (for example, refer to Patent Document 1).
The wavelength of the excitation light necessary for bringing a substance from the ground state to an excited state and the wavelength of the fluorescence which the substance emits when returning from the excited state to the ground state depend on the kind of substance. Accordingly, in a measurement using a fluorescence measurement device, the excitation wavelength to be used in the measurement and the fluorescence wavelength to be detected with the photodetector must be appropriately set for the component to be detected (i.e. objective component). In a measurement using a conventional fluorescence measurement device, the optimal excitation and fluorescence wavelengths for detecting the objective component are previously determined as follows:
(1) With only a solvent present in a sample cell, a spectrum showing the fluorescence intensity at each fluorescence wavelength is obtained by varying the fluorescence wavelength while maintaining the excitation wavelength at a fixed value. (This spectrum is hereinafter called the “fluorescence-side spectrum.”)
(2) With an objective component and the solvent present in the sample cell, a fluorescence-side spectrum is similarly obtained.
(3) The fluorescence-side spectrum of the objective component is obtained by subtracting the spectrum obtained in Step (1) from the spectrum obtained in Step (2), and the wavelength at which the fluorescence intensity is maximized in the obtained spectrum is selected as the optimal fluorescence wavelength.
(4) With only the solvent present in the sample cell, a fluorescent spectrum showing the fluorescence intensity at each excitation wavelength is obtained by varying the excitation wavelength while maintaining the fluorescence wavelength at a fixed value. (This spectrum is hereinafter called the “excitation-side spectrum.”)
(5) With the objective component and the solvent present in the sample cell, an excitation-side spectrum is similarly obtained.
(6) The excitation-side spectrum of the objective component is obtained by subtracting the spectrum obtained in Step (4) from the spectrum obtained in Step (5), and the wavelength at which the fluorescence intensity is maximized in the obtained spectrum is selected as the optimal excitation wavelength.
It should be noted that the measurements of the fluorescence-side spectrum and the excitation-side spectrum may be performed in reverse order.
By the previously described method, the excitation wavelength and the fluorescence wavelength at which the highest fluorescence intensity is obtained can be respectively selected as the optimal excitation wavelength and the optimal fluorescence wavelength.
On the other hand, an absorbance determination device normally has an irradiation optical system for separating a predetermined wavelength of light from the light generated by a light source and irradiating a sample with the separated light as the irradiation light and a photodetector for detecting the light that has passed through the sample (transmission light) and producing a signal corresponding to the amount of the detected light.
The wavelength of the light absorbed by a substance depends on the kind of substance. Accordingly, in a measurement using an absorbance determination device, the wavelength of the irradiation light used in the measurement must be appropriately set for the component to be detected (i.e. objective component). Therefore, in a measurement using a conventional absorbance determination device, it is necessary to obtain information about the absorption wavelength of the objective component beforehand by referring to an appropriate document or the like, or to determine the optimal wavelength for the measurement of the objective component as follows:
(1) With only a solvent present in a sample cell, an absorption spectrum is obtained by varying the wavelength of the irradiation light.
(2) With the objective component and the solvent present in the sample cell, an absorption spectrum is similarly obtained.
(3) The absorption spectrum of the objective component is obtained by subtracting the spectrum obtained in Step (1) from the spectrum obtained in Step (2), and the wavelength at which the absorbance is maximized in the absorption spectrum is selected as the optimal wavelength.